Dementia is an umbrella term for a collection of symptoms that result from damage to the brain caused by different disease - for example Alzheimer’s.

Some early symptoms associated with the degenerative disease that may appear some time before a diagnosis include memory loss, difficulty concentrating, struggling to follow a conversation or find the right word and mood changes.

But now scientists have found a fitful night’s sleep and a habit of daytime catnapping could be an early warning sign of Alzheimer’s disease.

Restless nights and sleepy days are a common pattern in patients with Alzheimer’s disease, according to new research conducted in humans and mice.

The study published in the journal JAMA Neurology found that in older people who show no signs of cognitive impairment, those with a sleep-wake cycle that is subtly off-kilter are more likely to have amyloid protein deposits in their brain.

Amyloid “plaques” are a hallmark of Alzheimer’s and can develop years before dementia symptoms appear.

Participants of the study whose sleep patters were more regular were found less likely to have significant clumps of amyloid protein in their brains.

While the research discovered more amyloid in people who have a disturbed sleep pattern, the findings can not answer for definite if restless sleep actually contributes to the development of Alzheimer’s or just a sign of the disorder.

Study co-author Dr Erik S. Musiek, a Washington University neurologist who studies the role of the circadian clock on ageing, said: “I don’t want to scare people into thinking that if they wake up often at night they’ll have Alzheimer’s.”

Some changes in sleep are typical as people age. But while disrupted sleep patterns generally manifest themselves as night-time awakenings and short bursts of compensating daytime sleep, participants didn’t always notice or report these occurrences.

Dr Musiek added: “These are subtle things, and we can detect them in a large group of people.”

How can you stave off dementia?

Keeping fit in older age helps stave off Alzheimer’s disease, according to other research.

Scientists have discovered that bursts of exercise, such as a bike ride or a brisk walk, boost “white matter” tissue found deep within the brain.

This matter contains the crucial nerve fibres which relay messages to and from the brain, maintaining cognitive functions and memory.

Currently there is no known cure for Alzheimer’s which causes nerve cell death and loss of tissue throughout the brain, leading to dementia. As the disease takes hold the brain shrinks dramatically, affecting most of its functions.